Refrigerant compressor

ABSTRACT

Hermetically encapsulated refrigerant compressor ( 1 ), comprising a cylinder housing ( 3 ), which is used as the basis for manufacturing various refrigerant compressor construction series each having different working volumes and a piston ( 6 ) guided in a piston bore ( 8 ) of the cylinder housing ( 3 ) along a defined piston run surface ( 9 ). According to the invention, it is provided that a free run section ( 10 ) is situated in the piston bore ( 8 ) as a function of the particular working volume to be implemented inside the cylinder housing ( 3 ), which working volume is fixable by a variation of the position of the piston ( 6 ) or the piston run surface ( 9 ) in the piston bore ( 8 ), so that the piston run surface ( 9 ) is reduced to a minimal guide length measured in the direction of the cylinder axis ( 12 ), at which the piston ( 6 ) is only lowered in its bottom dead center position far enough into the area of the piston bore ( 8 ) corresponding to the piston run surface ( 9 ) so that the piston ( 6 ) is just prevented from falling out of the piston bore ( 8 ) and a sealing action of the piston ( 6 ) in relation to the piston run surface ( 9 ) is provided.

AREA OF THE INVENTION

The invention relates to a hermetically encapsulated refrigerant compressor, comprising a cylinder housing as the basis for manufacturing various models of a refrigerant compressor family and a piston, which is guided in a piston bore of the cylinder housing along a defined piston run surface, for compressing a working medium, which piston is linked using a connecting rod to a crankshaft, which is driven by an electric motor, the crankshaft, which is rotatable around a rotational axis, being mounted in a mounting body which is preferably implemented integrally with the cylinder housing, the piston bore being closed in a first end area by a cylinder head comprising a valve plate, while the piston bore is open in a second end area facing toward the crankshaft to receive the piston, and the piston bore has a free run section, which adjoins the piston run surface and is situated in the second end area of the piston bore facing toward the crankshaft, whose clear opening width is greater than the diameter of the piston run surface, in order to prevent a contact between piston and cylinder housing in this section during the operating positions of the piston, according to the preamble of Claim 1.

PRIOR ART

The refrigerator process using zeotropic gases per se has been known for some time. The refrigerant is heated in a vaporizer by absorbing energy from the space to be cooled and finally overheated, which results in vaporization, and is compressed to a higher pressure level using a piston-cylinder unit of the refrigerant compressor, where it discharges heat via a condenser and is conveyed back into the vaporizer via a throttle, in which pressure reduction and cooling of the refrigerant occur. Such refrigerant compressors are used in the household and industrial fields, where they are typically situated on the rear side of a refrigerator or refrigerated shelf.

The refrigerant compressor, which has a hermetically sealed compressor housing, comprises an electric motor, which drives a piston oscillating in a piston bore of a cylinder housing via a crankshaft to compress the refrigerant. It is typical to implement the cylinder housing integrally in the form of a mounting body which is fastenable on the stator of the electric motor, and which also has a main bearing to accommodate the crankshaft. Alternatively thereto, the cylinder housing can also be manufactured as a separate part and can be fastened on the mounting body.

The piston bore of the cylinder housing is closed in a first axial end area by a valve plate or by a cylinder head, while the piston bore is open to accommodate the piston or is penetrated by the connecting rod in the installed state of the refrigerant compressor in a second end area facing toward the crankshaft.

In order to reduce the friction of the piston during its working strokes as much as possible, it is desirable for the piston run surface, i.e., the surface formed by the piston bore on which the piston contacts the cylinder housing or (because of the required lubricant film) is guided by the cylinder housing with slight play, to be kept as small as possible. The piston therefore preferably protrudes out of the piston bore in its bottom dead center position or the lateral surface of the piston only partially contacts the piston run surface.

In the course of efficient mass production of refrigerant compressors according to the species, the requirement exists that a described cylinder housing or a mounting body having the cylinder housing can be installed in a plurality of refrigerant compressor production series, which differ from one another in design, in particular with respect to the size of the working volume of the piston-cylinder configuration.

To implement a working volume within the cylinder housing which corresponds to the performance data of a particular production series model, the cylinder housing or the crankshaft is equipped with pistons and connecting rods of different sizes. The piston plunges to different depths into the piston bore through a specific selection of the piston and connecting rod lengths (each measured along the cylinder axis).

According to the prior art, in this case the distance between the rotational axis of the crankshaft and the beginning of the piston run surface of the cylinder housing facing toward the crankshaft remains unchanged, i.e., the second end area of the piston bore is also not changed if connecting rods or pistons of different lengths are used in the cylinder housing. In order to perform a corresponding working space adaptation, in contrast, the first end area of the piston bore facing toward the cylinder head is shortened or the initially oversized cylinder housing is axially shortened in the area intended for contact of the cylinder head or the valve plate using a machining method, e.g., using milling.

After the cylinder housing or the piston bore has been shortened in the first end area by an amount corresponding to the particular desired working volume, the valve plate, including the cylinder head, is fastened on the recently machined front side of the cylinder housing.

In the case of special pre-installations of the cylinder head and the valve plate on the cylinder housing, in particular in the case of a screwless cylinder head fastening device known from EP 1888918 A1, however, described machining or shortening of the cylinder housing on the cylinder head side does not come into consideration or would be viewed as uneconomical, since the cylinder housing is provided with precisely manufactured fixing grooves in this area, in which corresponding fixing elements engage in a locking manner.

Alternatively to an adaptation of the axial length of the cylinder housing or the piston bore, it would also be possible to produce the particular desired working volume by an adaptation of the piston bore diameter or the entire piston run surface provided inside the cylinder housing. In such a case, the piston bore diameter could be expanded by boring out and also a correspondingly larger dimensioned piston or a piston having a larger piston diameter could be inserted into the bored-out piston bore of the cylinder housing. However, manufacturing of pistons having diameters of different sizes, which is required in this case, is complex and uneconomical. The precisely fitted final machining of the bored-out piston bore in the area of the piston run surface also requires a high manufacturing effort.

It is therefore the object of the present invention to propose a simple possibility for implementing different working volumes of a cylinder housing situated on a mounting body, without the piston diameter having to be adapted to the required working volume and without processing/shortening of the cylinder housing or the piston bore on the cylinder head side having to be performed. In this case, the friction of the piston on the piston guide surface of the cylinder housing is to be reduced to a minimum and the wear and the performance losses of refrigerant compressors according to the species are thus to be reduced.

In particular, the cylinder housing or the mounting body is to be able to be equipped with pistons and connecting rods of different lengths, the piston run surface, i.e., the area of the cylinder housing which the piston wipes during its working stroke, being implemented as small as possible in each case.

It is a further object of the present invention to propose an advantageous installation of a piston bolt which links the piston to the connecting rod, in order to allow a plurality of constructive design possibilities for implementing the piston-cylinder configuration, in particular for dimensioning the pistons, connecting rods, and crankshafts.

SUMMARY OF THE INVENTION

These objects are achieved according to the invention by a hermetically encapsulated refrigerant compressor having the characterizing features of Claim 1. A refrigerant compressor according to the species of a refrigerant compressor construction series comprises a cylinder housing and a piston guided in a cylinder bore of the cylinder housing along a defined piston run surface for compressing a working medium, which piston is linked using a connecting rod to a crankshaft driven by a electric motor, the crankshaft, which is rotatable around a rotational axis, being mounted in a mounting body preferably implemented integrally with the cylinder housing, and the piston bore being closed in the first end area by a valve plate or a cylinder head, while the piston bore is open to accommodate the piston in a second end area facing toward the crankshaft and the piston bore has a free run section adjoining the piston run surface situated in the second end area of the piston bore facing toward the crankshaft, whose clear opening width is greater than the diameter of the piston run surface, to prevent contact between piston and cylinder housing in this section during the operating positions of the piston or during the piston oscillation.

It is provided according to the invention that the free run section is situated as a function of a particular working volume, which is delimited by the valve plate and the front side of the piston, and which is fixable by a variation of the position of the piston or the piston run surface in the piston bore, to be implemented inside the cylinder housing in such a way that the piston run surface is reduced in each case to a minimal guide length, at which the piston is only lowered far enough in its bottom dead center position into the area of the piston bore corresponding to the piston run surface that the piston is just prevented from falling out of the piston bore and a sealing action of the piston in relation to the piston run surface is provided.

A cylinder housing of the mounting body, which is produced in a standard manner and is not yet defined or is oversized with respect to its working volume, can therefore be used as the basis for manufacturing various refrigerant compressor construction series, which differ from one another in particular with respect to the size of the working volume. The manufacturing costs of the members of such refrigerant compressor construction series may therefore be kept very economical.

The clear cross-section or the diameter measured orthogonally to the cylinder axis is thus greater than the piston bore diameter in the area of the piston run surface. In that the piston run surface is reduced to a particular desired longitudinal extension by providing the free run section according to the invention, unnecessary friction of the piston on the cylinder housing can be reduced and the effective performance of the refrigerant compressor can thus be increased. The cylinder housing or the mounting body can be equipped with pistons and connecting rods of various lengths in this case, the piston run surface of the cylinder housing wiped by the piston during its working strokes being able to be optimized in a friction aspect, i.e., being able to be kept as small as possible.

A further advantage of the invention is that joining of the piston in the cylinder from the side of the cylinder facing toward the crankshaft is made easier by the free run section having its greater clear width in comparison to the diameter of the piston run surface.

The transition between the free run section and the piston run surface of the cylinder housing is implemented in a preferred embodiment variation of the invention using a chamfer, a radius, or a chamfer-radius combination, which in turn promotes the joining of the piston and the sliding of the piston beyond the piston run surface.

In a preferred embodiment variant of the invention, the free run section is implemented, in a manner which is simple to manufacture, as a recess in the cylinder housing which is rotationally symmetric to the cylinder axis.

The design of the free run section in the cylinder housing so that the piston run surface has a minimal guide length measured in the direction of the cylinder axis or the axial direction of the piston bore has the advantage that the piston, in its bottom dead center position, is only lowered enough into the area of the piston bore corresponding to the piston run surface so that the piston is prevented from falling out of the piston bore and a sufficient sealing action of the piston in relation to the piston run surface is provided. The overlap area of the lateral surface of the piston with the piston run surface of the cylinder housing viewed in the bottom dead center position of the piston is thus selected as just large enough that a reliable seal of the cylinder chamber bounded by the front side of the piston and the valve plate is ensured, while the piston partially protrudes beyond the crankshaft-side end area of the piston run surface.

In that the piston run surface is reduced to a minimal guide surface and the piston thus partially protrudes beyond the guide surface, the advantage further results that a shorter connecting rod can be used than in the case of completely lowering the piston, which is located in its bottom dead center position, within the piston run surface. A connecting rod whose length is selected as short as possible allows a smaller overall size of the refrigerant compressor. The space savings thus made possible within the compressor housing can also be used for the purpose of enlarging the rotor of the electric motor, which is connected to the crankshaft, so that a higher torque of the crankshaft is achievable.

A standard manufactured piston bore can be expanded by mechanical machining in its second end area facing toward the crankshaft depending on the usage requirement so that the guide length is reduced to a particular possible minimum.

Such a variation of the position of the piston or the piston run surface in the piston bore can be performed by a corresponding adaptation of the geometry of the piston-cylinder configuration. In a particularly preferred embodiment variant of the invention, the position of the piston or the piston run surface is varied via a use of connecting rods and/or pistons dimensioned in different lengths (as a function of the particular desired working volume). It is obvious that the length of the pistons and connecting rods is measured in the oscillation direction of the piston in this case.

The variation of the piston or the piston run surface in the piston bore can also be performed by a variation of the eccentricity of a crank pin, which links the connecting rod to the crankshaft, in relation to the rotational axis of the crankshaft.

In order to ensure that the piston does not contact the cylinder housing in the free run section, it is provided according to a preferred embodiment variant of the invention that the clear cross-sectional width of the free run section is greater by more than 2/100 mm, preferably by more than 1/10 mm, than the piston bore diameter.

According to a further preferred embodiment variant of the invention, it is provided that the cylinder housing has a first installation opening running essentially perpendicularly to the cylinder axis, the center axis of this installation opening being situated offset by a distance amount in the direction of the first end area of the piston bore to a piston bolt axis of a piston located in its bottom dead center position. The first installation opening is preferably used for the purpose of inserting a counter holding tool into the piston bolt hole and thus determining the location of the piston bolt within the piston bolt hole. The first installation opening can also be used, however, to insert the piston bolt itself into the piston bolt hole.

By installing the piston bolt in a piston located above its bottom dead center position, greater design freedom is made possible for the dimensioning of individual components of the piston-cylinder configuration. In particular, connecting rods and pistons of various lengths and differently dimensioned crankshafts may be used, friction optimization of the piston run surface always being able to be performed by the above-described provision according to the invention of a free run section.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be explained in greater detail on the basis of an exemplary embodiment. In the figures:

FIG. 1 shows a sectional view of a refrigerant compressor according to the invention

FIG. 2 shows an isometric detail view of a mounting body according to the invention manufactured integrally with a cylinder housing

FIG. 3 shows a vertical section through the mounting body according to the invention from FIG. 2

FIG. 4 shows a top view of the mounting body according to the invention from FIG. 2

FIG. 5 shows a bottom view of the mounting body according to the invention from FIG. 2

FIG. 6 shows a side view of the mounting body according to the invention from FIG. 2

FIG. 7 shows a mounting body having a comparatively large working volume, a piston guided in a piston bore being located in its bottom dead center position, in a top view

FIG. 8 shows a sectional view of the mounting body from FIG. 7 along line A-A

FIG. 9 shows a mounting body having a comparatively small working volume, a piston guided in a piston bore being located in its bottom dead center position, in a top view

FIG. 10 shows a sectional view of the mounting body from FIG. 9 along line A-A

FIG. 11 shows a detail “A” from FIG. 10

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

A refrigerant compressor according to the invention having a hermetically sealed compressor housing 14 is shown in FIG. 1. An electric motor 13, which is mounted using a spring-loaded bearing unit 27 in the floor area of the compressor housing 14, is situated inside the compressor housing 14.

A bridge-shaped mounting body 2, which is fastened on the stator 13 a of the electric motor 13 using screw elements 29, is placed on the electric motor 13. The mounting body 2 shown in a detail view in FIG. 2 spans the upper part of a motor winding 34 of the electric motor 13 (also referred to as the “upper winding head”) and has two diametrically opposing support base elements 31 and 32, which are supported on the stator 13 a. Each of the support base elements 31, 32 has two bearing pedestals 31 a, 31 b or 32 a, 32 b, respectively, at the ends, so that the relatively narrow mounting body 2 thus rests stably on the stator 13 a on a total of four bearing surfaces (see a bottom view of the mounting body 2 according to FIG. 5).

Each support base element 31, 32 is provided with a threaded hole 33. The stator 13 a of the electric motor 13 is provided with through holes 30, which run essentially vertically in the operating position of the refrigerant compressor 1, through which screw elements 29 can be guided and screwed into the threaded holes 33 of the mounting body 2. Screw heads 29 a of the screw elements 29 facing toward the floor area of the compressor housing 14 are inserted into the spring-loaded bearing units 27, so that the electric motor 13, including the mounting body 2 fastened thereon, is held in a particular desired operating position.

The mounting body 2 is implemented integrally with a cylinder housing 3, which is used to receive a piston 6 guided in a piston bore 8 of the cylinder housing 3, using which a refrigerant, which is conveyed into the compressor housing 14 and removed therefrom again via supply and drain lines 35 in a known manner, is compressed.

A main bearing 4 in the form of a plain bearing, which is provided to receive a crankshaft 5, is implemented in a middle section 2 a of the mounting body 2 located between the support base elements 31, 32. The rotational axis 11 of the crankshaft 5 or the axis of symmetry of the bush-shaped main body runs orthogonally to the cylinder axis 12 (see FIG. 3).

The shaft 5 a of the crankshaft 5 is connected to a rotor 13 b and is set into rotation by a corresponding stator commutation, so that the piston 6, which is linked using a connecting rod 7 to the crankshaft 5, oscillates along the cylinder axis 12.

For this purpose, the connecting rod 7 has a first end section provided with a first connecting rod eye 7 a and a second end section provided with a second connecting rod eye 7 b, and a shaft section 7 c which connects the two end sections to one another. The first connecting rod eye 7 a is linked on a crank pin 19 of an eccentric cheek 18 of the crankshaft 5, while the second connecting rod eye 7 b is linked using a piston bolt 23 to the piston 6.

The piston bore 8 of the cylinder housing is closed in a first end area 8 a by a valve plate 16, while the piston bore 8 is open to accommodate the piston 6 or is penetrated by the connecting rod 7 in a second end area 8 b facing toward the crankshaft 5.

The piston 6 completes a particular defined piston stroke x within the piston bore 8, the piston stroke x being understood as the distance by which a front side 6 a of the piston 6 facing toward the valve plate 16 is displaced during a working stroke, i.e., a movement from the bottom dead center position into the top dead center position of the piston 6.

The valve plate 16 is fastened in the present exemplary embodiment using a specially designed cylinder head 15 on the cylinder housing 3. The cylinder head 15 and the valve plate 16 are fastened without screws on the cylinder housing 3, the cylinder head 15 being clamped using one or more clamp-shaped fixing elements 17 on the cylinder housing 3 or being locked thereto. In this case, the essentially cylindrical outer jacket of the cylinder housing 3 is provided with a holding groove 26, which is obvious in FIGS. 2 and 3, and in which the fixing element 17 engages.

Such a cylinder head configuration is pre-installed in mass production and is no longer to be changed, in particular, the area of the cylinder housing 3 on the cylinder head side is not to be subsequently milled, as is typically performed for working volume modification of the cylinder housing 3.

Independently of the selection of the length of the connecting rod 7 and the length of the piston 6, which is measured in the oscillation direction of the piston 6, i.e., independently of how deep the piston 6 plunges into the piston bore 8 during its working stroke, the friction of the piston 6 in the cylinder housing 3 is to be reduced as much as possible. Such an optimization of the friction behavior of the piston 6 is achieved in that the piston run surface 9—this is the surface formed by the piston bore 8 on which the piston 6 contacts the cylinder housing 3 or wipes it with slight play—is kept as small as possible, so that the piston 6 partially protrudes out of the piston bore 8 or out of the piston run surface 9 in its bottom dead center position, shown in FIGS. 7 and 8. In FIG. 8, a piston 6 in its bottom dead center position, is shown in a purely exemplary manner, whose lateral surface is only enclosed approximately three-fourths by the cylinder bore 8 or the piston run surface 9, while approximately one-fourth of the piston lateral surface protrudes out of the cylinder bore 8, i.e., is not guided by the cylinder housing 3.

There are multiple design possibilities to change the working volume, which is delimited by the valve plate 16 (not shown in FIG. 8) and the front side 6 a of the piston 6, within the cylinder housing 3. The working volume can be established as a function of the characteristics of a particular refrigerant compressor model via a variation of the position of the piston 6 or the position of the piston run surface 9 in the piston bore 8.

The working volume or the position of the piston 6/the piston run surface 9 is preferably changed by a variation of the length of the connecting rod 7 or the connecting rod shaft 7 c.

A change of the working volume or the position of the piston 6/the piston run surface 9 in the piston-cylinder configuration 28 shown in FIG. 8 may also be performed in that the geometry of the crankshaft 5 is changed, for example, in that the eccentricity of the crank pin 19 or the distance of the axis 20 of the crank pin 19, which is situated on the eccentric cheek 18, to the rotational axis 11 of the crankshaft 6 is increased or decreased. In such a case, the length of the piston stroke x would also change.

A change of the working volume or the position of the piston 6/the piston run surface 9 could also be performed by a modification of the piston geometry or by a change of the piston length (measured parallel to the cylinder axis 12).

Independently of the concrete component modifications by which a change of the working volume is performed, the piston run surface 9 of the cylinder bore 8 is also displaced or it is shortened or lengthened similarly to the change of the working volume.

Solely as an example, a piston-cylinder configuration 28 is shown in FIG. 8 having a relatively large longitudinal extension z of the working volume measured along the cylinder axis 12, while a piston-cylinder configuration 28 having a relatively small working volume longitudinal extension z measured along the cylinder axis 12 is shown in FIG. 10.

For example, if the longitudinal extension z of the working volume of the piston-cylinder configuration 28 shown in FIG. 8 were changed in such a manner that a longer connecting rod 7 was used and also the distance of the axis 20 of the crank pin 19 situated on the eccentric cheek 18 on the crankshaft 5 was also adapted to the rotational axis 11 of the crankshaft 5, this would have the result that the piston 6 would also plunge deeper into the piston bore 8 during its bottom dead center position and the entire lateral surface of the piston 6 would be enclosed by the piston bore 8 in this case.

It is obvious that a modification or expansion of the working volume provided inside the cylinder housing 3 can still also be performed by a corresponding variation of the piston bore diameter 8′ or by boring out the piston bore 8.

As already described in the introduction, however, a contact of the entire piston lateral surface by the cylinder housing 3 would be disadvantageous with respect to friction efficiency, since it would suffice in the bottom dead center position of the piston 6 if the piston 6 were only lowered partially into the piston bore 8 of the cylinder housing 3.

It is provided according to the invention that the piston bore 8 has a free run section 10, which adjoins the piston run surface 9 and is situated in the second end area 8 b of the piston bore 8 facing toward the crankshaft 5, and whose clear opening width or whose diameter 10′ is greater than the diameter 9′ of the piston run surface 9.

The diameter 8′ of the piston bore 8 or the diameter 9′ of the piston run surface 9 is thus expanded in the second end area 8 b by a free run section 10, in which the cylinder housing 3 is not contacted by the piston 6 during the piston oscillation, which is executed in its operating state (see FIG. 10 and FIG. 11).

The free run section 10 according to the invention can be implemented, for example, as a recess in the cylinder housing 3 which is rotationally symmetric to the cylinder axis 12 (thus obvious in FIG. 10 or FIG. 11).

Instead of a concentric configuration of the free run section 10 to the piston bore 8, any other desired configuration and geometric design of the free run section 10 can also be performed. The free run section 10 can also be implemented as a chamfer on the inner side of the cylinder housing 3 corresponding to the piston bore 8.

In any case, the piston bore 8 has an expanded section in the second end area 8 b facing toward the crankshaft 5, whose clear cross-sectional width 10′ is greater than the piston bore diameter 8′ in the area of the piston run surface 9 or than the piston run surface diameter 9′.

The free run section 10 is preferably situated in the cylinder housing 3 so that the piston run surface 9 has a minimal guide length (measured in the direction of the piston oscillation or parallel to the cylinder axis 12). In case of such a minimal guide length, the piston 6 is only lowered, in its bottom dead center position, far enough into the area of the piston bore 8 corresponding to the piston run surface 9 that the piston 6 is prevented from falling out of the piston bore 8 and a sufficient sealing action of the piston 6 in relation to the piston run surface 9 is provided, i.e., a reliable seal of the cylinder chamber delimited by the front side 6 a of the piston 6 and the valve plate 16 is ensured. The piston 6 is prevented from falling out of the piston bore 8 as long as at most half of the axial length of the piston 6, in its bottom dead center position, protrudes beyond the piston run surface 9.

Through the provision of the free run section 10 according to the invention, whose longitudinal extension 10″ measured in the oscillation direction of the piston 6 or parallel to the piston run surface 9 is thus selected so that the piston run surface 9 is reduced to a minimum guide length, the lateral surface of the piston 6 is in turn partially exposed in its bottom dead center position. In the case of a piston-cylinder configuration 28 according to FIG. 10, in which the piston 6 is plunged relatively deep into the piston bore 8 and the piston run surface 9 is adjacent to the first end area 8 a of the piston bore 8 on the cylinder head side, the same friction advantage results as in the case of a configuration according to FIG. 8, in which the piston run surface 9 overlaps the second end area 8 b of the piston bore 8 and the piston partially protrudes out of the cylinder housing 3.

The distance of the beginning of the piston run surface 9, facing toward the crankshaft 3, to the rotational axis 11 of the crankshaft is thus no longer constant (as in the prior art), but rather variable as a function of the positioning of the free run section 10 according to the invention.

Is thus possible to provide a cylinder housing 3, which is oversized with respect to its axial longitudinal extension, or a standard mounting body 2, having such a cylinder housing 3, for a plurality of refrigerant compressor models which differ from one another through a differing working volume of their piston-cylinder configurations 28. The cylinder housing 3 or mounting body 2 may further be adapted in each case so that the lateral surface of the piston 6 is partially exposed in its bottom dead center position using the free run section or the piston run surface 9 is reduced to the minimal guide length.

It is to be noted that the illustration of the cylinder head 15 and the valve plate 16 situated in the first end area 8 a of the piston bore 8 was dispensed with.

The production of the free run section 10 or the expansion of the piston bore 8 can be performed by suitable machining methods such as boring, turning, or milling. The free run section 10 is preferably produced by simple boring out of the piston bore 8 to an enlarged diameter.

The clear cross-sectional width 10′ of the free run section 10 is greater in this case by more than 2/100 mm, preferably by more than 1/10 mm than the piston bore diameter 8′. A simple installation of the piston 6 in the cylinder housing 3 from the side of the crankshaft-side second end area 8 b of the piston bore 8 is made possible in that the clear cross-sectional with 10′ of the free run section 10 is preferably greater by more than 1 mm than the piston bore diameter 8′.

Furthermore, the installation of the piston 6 from the second piston bore end area 8 b in the cylinder housing 3 is promoted by the design of a corresponding transition between the free run section 10 and the piston run surface 9 of the cylinder housing 3. Such a transition is preferably implemented using a chamfer 38 (shown by dashed lines in a detail view according to FIG. 11) or a radius 39. The chamfer 38 or the radius 39 preferably runs concentrically to the cylinder axis 12.

It is to be noted that the cylinder housing 3 can also be implemented in multiple parts, to achieve manufacturing economy advantages. Thus, for example, insert elements provided for accommodating the piston 6 may be provided, which are inserted into corresponding recesses (following the cylinder axis 12) in the cylinder housing 3, preferably pressed in or also fixed by another type of fastening technology. Such insert elements can be cylindrical bushes, for example, whose axial length is dimensioned so that all configurations of the piston-cylinder configuration 28 according to the invention as described above and shown in FIGS. 1-11 may be implemented. Such insert elements have a hole (running along the cylinder axis 12 in the installed position in the cylinder housing 3), by which the piston run surface 9 is formed. The insert element can either form only the piston run surface 9 or also the free run section 10, i.e., it can have a corresponding transition or step jump.

A particularly advantageous installation of the above-mentioned piston bolt 23, which links the piston 6 on the connecting rod 7, in a corresponding piston bolt hole 22 of the piston 6, is achieved in that the piston bolt 23 is inserted into the piston bolt hole 22 in a position in which the piston 6 was displaced in the direction of the cylinder head 15 in relation to its bottom dead center position (see FIG. 1).

In this case, the cylinder housing 3 has a first installation opening 24, which runs essentially perpendicularly to the cylinder axis 12 and is best visible in FIG. 3, the central axis 25 of this first installation opening 24 being displaced by a distance amount y (shown in FIG. 1) in the direction of the first end area 8 a of the piston bore 8 to the piston bolt axis 21 of the piston 6, which is located in its bottom dead center position.

A counter holding tool (not shown) can be inserted into this first installation opening 24, this tool penetrating up to a particular desired depth or end position into the piston bolt hole 22 and offering a stop for the piston bolt 23, which is inserted from a diametrically opposing side of the cylinder housing 3 into the piston bolt hole 22 and into the second connecting rod eye 7 b of the connecting rod 7. The connecting rod 7 or its second connecting rod eye 7 b is lowered in this case into a connecting rod receptacle 36 provided inside the piston 6.

In that the counter holding tool, which is inserted into the first installation opening 24 or into the piston bolt hole, fixes the piston 6 in a position inside the cylinder housing 3, in which the piston bolt axis 21 is aligned with axis 25 of the first installation opening 24, the piston bolt 23 can be brought into its operating position according to FIG. 3 or pressed into the cylinder housing 3 from the side of a second installation opening 37, which is diametrically opposite to the first installation opening 24. The stop formed by the counter holding tool is further required for the purpose of fixing the piston bolt 23 in its operating position using a fixing pin (optionally provided, not shown).

The second installation opening 37 can be a through hole in the cylinder housing 3 running orthogonally to the cylinder axis 12 or also any other desired opening. It is to be noted that the first installation opening 24 can also be used for inserting the piston bolt 23 into the piston bolt hole 22.

Through an installation according to the invention of the piston bolt 23 into a piston 6 located above its bottom dead center position, greater design freedom is made possible for the constructive design of the piston-cylinder configuration 28 or for situating the free run section 10 according to the invention and the piston run surface 9 inside the cylinder housing 3.

LIST OF REFERENCE NUMERALS

-   1 refrigerant compressor -   2 mounting body -   3 cylinder housing -   4 main bearing for crankshaft -   5 crankshaft -   6 piston -   6 a front side of the piston -   6′ piston length -   7 connecting rod -   7 a first connecting rod eye -   7 b second connecting rod eye -   7 c shaft section of the connecting rod -   8 piston bore -   8 a first end area of the piston bore -   8 b second end area of the piston bore -   8′ diameter of the piston bore -   9 piston run surface -   9′ diameter of the piston run surface -   10 free run section -   10′ clear opening width of the free run section -   10″ longitudinal extension of the free run section -   11 crankshaft axis -   12 cylinder axis -   13 electric motor -   13 a stator -   13 b rotor -   14 compressor housing -   15 cylinder head -   16 valve plate -   17 fixing elements for cylinder head -   18 eccentric disc -   19 crank pin -   20 axis of the crank pin -   21 piston bolt axis -   22 piston bolt hole -   23 piston bolt -   24 first installation opening -   25 axis of the installation opening -   26 holding element -   27 mounting unit for electric motor -   28 piston-cylinder configuration -   29 screw elements -   30 through hole -   31 first support base element -   31 a first bearing pedestal of the first support base element -   31 b second bearing pedestal of the first support base element -   32 second support base element -   32 a first bearing pedestal of the second support base element -   32 b second bearing pedestal of the second support base element -   33 threaded holes -   34 upper winding head of the motor winding -   35 supply and drain lines -   36 connecting rod receptacle -   37 second installation opening -   38 chamfer -   39 radius -   x piston stroke -   y distance amount between the central axis 25 of the installation     opening 24 and the piston bolt axis 21 -   z longitudinal axis of the working chamber 

1. A hermetically encapsulated refrigerant compressor (1), comprising a cylinder housing (3), which is used as the basis for manufacturing various refrigerant compressor construction series each having different sizes of the working volume, and a piston (6), which is guided in a piston bore (8) of the cylinder housing (3) along a defined piston run surface (9), for compressing a working medium, which piston is linked using a connecting rod (7) to a crankshaft (5) driven by an electric motor (13), the crankshaft (5), which is rotatable around a rotational axis (11), being mounted in a mounting body (2), and the piston bore (8) being closed in a first end area (8 a) by a cylinder head (15) comprising a valve plate (16), while the piston bore (8) is open to accommodate the piston (6) in a second end area (8 b) facing toward the crankshaft (5), the piston bore (8) having a free run section (10) adjoining the piston run surface (9) and situated in the second end area (8 b) of the piston bore (8) facing toward the crankshaft (5), whose clear open width (10′) is greater than the diameter (9′) of the piston run surface (9), in order to prevent a contact between piston (6) and cylinder housing (3) in this section during the operating positions of the piston (6), wherein the free run section (10) is situated, as a function of the particular working volume to be implemented, within the cylinder housing (3), which working volume is fixable by a variation of the position of the piston (6) or the piston run surface (9) in the piston bore (8), so that the piston run surface (9) is reduced to a minimal guide length measured in the direction of the cylinder axis (12), in the case of which the piston 6 is only lowered in its bottom dead center position into the area of the piston bore 8 corresponding to the piston run surface (9), so that the piston (6) is just prevented from falling out of the piston bore (8) and a sealing action of the piston (6) in relation to the piston run surface (9) is provided.
 2. The hermetically encapsulated refrigerant compressor (1) according to claim 1, wherein the variation of the position of the piston (6) or the piston run surface (9) in the piston bore (8) is performed via a use of connecting rods 7 and/or pistons 6 dimensioned in different lengths.
 3. The hermetically encapsulated refrigerant compressor (1) according to claim 1 wherein the variation of the position of the piston (6) or the piston run surface (9) in the piston bore (8) is performed by a variation of the eccentricity of a crank pin (19), which links the connecting rod (7) on the crankshaft (3), in relation to the rotational axis (11) of the crankshaft (3).
 4. The hermetically encapsulated refrigerant compressor (1) according to claim 1, wherein the free run section (10) is implemented as a recess in the cylinder housing (3) which is rotationally symmetric to the cylinder axis (12).
 5. The hermetically encapsulated refrigerant compressor (1) according to claim 1, wherein the clear cross-sectional width (10′) of the free run section (10) is greater by more than 1/100 mm, preferably more than 1/10 mm, than the piston bore diameter (8′).
 6. The hermetically encapsulated refrigerant compressor (1) according to claim 1, wherein the piston run surface (9) merges into the free run section (10) via a chamfer (38) or a radius (39).
 7. The hermetically encapsulated refrigerant compressor (1) according to claim 1, wherein the cylinder housing (3) has a first installation opening (24) running essentially perpendicularly to the cylinder axis (12), the central axis (25) of this installation opening (24) being situated offset by a distance amount (y) in the direction of the first end area (8 a) of the piston bore (8) to a piston bolt axis (21) of a piston (6) located in its bottom dead center position.
 8. The hermetically encapsulated refrigerant compressor (1) according to claim 1, wherein the free run section (10) is produced by mechanical machining of the piston bore (8).
 9. The hermetically encapsulated refrigerant compressor (1) according to claim 1, wherein the mounting body (2) is implemented integrally with the cylinder housing (3). 